Sensor, composite material and method of manufacturing the same

ABSTRACT

A method of manufacturing a composite material, comprising providing a conductive polymer having a hydrophilic end and adding a metal oxide, such that the metal oxide is connected to the hydrophilic end of the conductive polymer, wherein the metal oxide is obtained by subjecting a metal oxide precursor to a dehydration reaction, a polymerization reaction, a condensation reaction, or a combination thereof.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of an application Ser. No. 15/862,634filed on Jan. 5, 2018, which claims the priority benefit of Chinaapplication serial no. 201710021060.5, filed on Jan. 11, 2017, and Chinaapplication serial no. 201711334995.5, filed on Dec. 14, 2017. Theentirety of each of the above-mentioned patent applications is herebyincorporated by reference herein and made a part of this specification

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention relates to a sensor, a composite material, and a method ofmanufacturing the same.

2. Description of Related Art

In recent years, due to the industrial development and the risingawareness of healthcare and environmental protection, sensingtechnologies, such as technologies of gas sensing, ultraviolet lightsensing, temperature sensing, humidity sensing and the like, are nowunder proactive development. In order to reduce the size and increasethe sensitivity of a sensor, interdigitated electrodes are commonly usedin the known sensor. However, in the case of a sensor with one hundredpairs of interdigitated electrodes, for example, the resistance of thesensor is still excessively high (approximately at the level of hundredsof Me), so the sensitivity of the sensor is still lower than expected.Hence, how to reduce the resistance of the sensor and facilitate thesensitivity thereof has become an issue to work on.

SUMMARY OF THE INVENTION

Embodiments of the invention provides a composite material suitable fora sensing material layer of a sensor. The composite material is capableof effectively reducing a resistance of the sensor and increasing asensitivity of the sensor.

One or some embodiments of the invention provide a sensor including afirst electrode, a second electrode, and a sensing material layer. Thesecond electrode and the first electrode are separated from each other.The sensing material layer is located between the first electrode andthe second electrode and covers the first electrode and the secondelectrode. The sensing material layer includes a conductive polymer anda metal oxide. The conductive polymer has a hydrophilic end. The metaloxide is connected to the hydrophilic end of the conductive polymer. Themetal oxide includes a metal oxide precursor.

One or some embodiments of the invention provides a composite materialsuitable for a sensing material of a sensor. The composite materialincludes a conductive polymer and a metal oxide. The conductive polymerhas a hydrophilic end and forms a colloidal particle in a solvent. Themetal oxide is connected to the hydrophilic end of the conductivepolymer.

One or some embodiments of the invention provide a method ofmanufacturing a composite material. The method includes the following: Aconductive polymer having a hydrophilic end is provided. A metal oxideis added, such that the metal oxide is connected to the hydrophilic endof the conductive polymer. The metal oxide is obtained by subjecting ametal oxide precursor to a dehydration reaction, a polymerizationreaction, a condensation reaction, or a combination thereof.

Based on the above, the composite material according to the embodimentsof the invention includes the conductive polymer and the metal oxide,and the metal oxide is connected to the hydrophilic end of theconductive polymer. Hence, in the composite material according to theembodiments of the invention, in addition to having a desirableconductivity, the hydrophilic ends of the conductive polymer do notreadily react with ambient water vapor and oxygen since the metal oxideblocks the hydrophilic ends of the conductive polymer. Therefore,conductive polymer degradation and coating inconvenience are alleviated.Besides, the composite material according to the embodiments of theinvention is applicable to a sensing material layer of a sensor. Thecomposite material is capable of effectively reducing the resistance ofthe sensor and increasing the sensitivity of the sensor.

In order to make the aforementioned and other features and advantages ofthe invention comprehensible, several exemplary embodiments accompaniedwith figures are described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1A is a schematic diagram of a composite material shown accordingto some embodiments of the invention.

FIG. 1B is an enlarged schematic diagram of a portion of the compositematerial shown according to FIG. 1A.

FIG. 2A is a schematic diagram of a composite material shown accordingto some other embodiments of the invention.

FIG. 2B is an enlarged schematic diagram of a portion of the compositematerial shown according to FIG. 2A.

FIG. 3 is a cross-sectional schematic diagram of an application of acomposite material for a solar cell shown according to some embodimentsof the invention.

FIG. 4 is a cross-sectional schematic diagram of an application of acomposite material in a sensor shown according to some embodiments ofthe invention.

FIG. 5 is a bar graph illustrating resistances of Experimental Examples1 to 3 and Comparative Examples 1 to 3.

FIGS. 6A to 6D are respectively optical microscopic photos ofComparative Example 1 and Experimental Examples 1 to 3.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts.

FIG. 1A is a schematic diagram of a composite material shown accordingto some embodiments of the invention. FIG. 1B is an enlarged schematicdiagram of a portion of the composite material shown according to FIG.1A.

Referring to FIG. 1A and FIG. 1B, a composite material 100 according toan embodiment of the invention includes a conductive polymer 110 and ametal oxide 120. The details are as follows.

The conductive polymer 110 may be a polymer carrying positive charge andnegative charge. In other words, the conductive polymer 110 has ahydrophilic end and a hydrophobic end. In some embodiments, the longcarbon chain (with hydrophobicity) of the conductive polymer 110 has aplurality of functional groups which are hydrophilic ends 112, such as acarboxyl group, hydroxyl group, sulfonic acid group, amino group, or acombination thereof, but the invention is not limited thereto. Forinstance, in some embodiments, the conductive polymer 110 is, forinstance, formed by one type of conductive polymer, wherein thehydrophobic long carbon chain of the conductive polymer 110 carries aplurality of the hydrophilic ends 112, and the hydrophilic ends 112 maybe connected to the metal oxide 120. In some other embodiments, theconductive polymer 110 is, for instance, formed by two types ofconductive polymers, wherein the long carbon chain is formed by aconductive polymer having a plurality of the hydrophilic ends 112 on aside chain, and the hydrophilic ends 112 may be connected to the othertype of conductive polymer having a plurality of hydrophobic ends 114,and may also be connected to the metal oxide 120, but the invention isnot limited thereto.

Specifically, the conductive polymer 110 includes a conjugated polymerand an acidic solubilizer. In an embodiment, the conjugated polymer maybe a main conductive structure, such as poly(3,4-ethylenedioxythiophene)(PEDOT), polyphenylene sulfide (PPS), polypyrrole (PPy), polythiophene(PT), polyaniline (PANT), or a combination thereof. The acidicsolubilizer may be poly(styrensulfonate) (PSS), acetic acid, propionicacid, butyric acid, benzoic acid, or a combination thereof. In someembodiments, the conjugated polymer (such as PEDOT) is not easilysoluble to a solvent (such as water). However, after the acid solublizeris added, the conductive polymer 110 (such as PEDOT:PSS) may bedispersed in an aqueous solution as a colloid or a colloidal particle.

In some embodiments, the conductive polymer 110 dispersed in the solventmay form a colloid particle. The solvent includes a polar solvent, suchas water, methanol, ethanol, propanol, isopropanol, butanol, ethyleneglycol, diethylene glycol, glycerol, propylene glycol, dipropyleneglycol, tripropylene glycol, or a combination thereof. The diameter ofthe colloidal particle formed by the conductive polymer 110 is, forinstance, between 10 nanometers and 500 nanometers. In some embodiments,the weight-average molecular weight (Mw) of the conductive polymer 110is, for instance, between 20000 g/mol and 500000 g/mol.

In a specific embodiment, the conductive polymer 110 is PEDOT:PSS, forexample. In the embodiment, PEDOT is the main conductive structure. PSSis P-type doped, and the hydrophilic ends 112 on the side chain of PSSare sulfonic acid groups carrying negative charge (SO₃ ⁻). The sulfonicacid groups carrying negative charge of PSS allows PEDOT to carrypositive charge (S⁺) and to be connected with S⁺ carrying positivecharge on PEDOT. In addition, PSS may also be connected with the metaloxide 120. In the embodiment, the ratio of PEDOT:PSS is, for instance,in a range from 1:1 and 1:10, but the invention is not limited thereto.

The metal oxide 120 may block the hydrophilic ends 112 of the conductivepolymer 110. In some embodiments, the metal oxide 120 is connected tothe hydrophilic ends 112 of the conductive polymer 110 to block thehydrophilic ends 112. In some embodiments, the size (diameter or length)of the metal oxide 120 is less than that of the conductive polymer 110.The metal oxide 120 is, for instance, titanium dioxide (TiO₂), tindioxide (SnO₂), zinc oxide (ZnO), tungsten trioxide (WO₃), iron oxide(Fe₂O₃), niobium pentoxide (Nb₂O₅), indium tin oxide (ITO), indiumtrioxide (In₂O₃), strontium titanate (SrTiO₃), nickel oxide (NiO),vanadium oxide (V₂O₅), molybdenum oxide (MoO₃), magnesium oxide,aluminum oxide, or a combination thereof.

In an embodiment, the metal oxide 120 is obtained by subjecting a metaloxide precursor to a dehydration reaction, a polymerization reaction, acondensation reaction, or a combination thereof. In an embodiment, themetal oxide precursor may be in the form of solution, and include atleast one metal ion and a ligand. Specifically, the metal oxideprecursor including the metal ion (such as titanium) and the ligand(such as isopropoxide) may be dissolved in a solvent (such as water)containing an auxiliary agent (such as an acid, an alkali, an oxidizer,or a combination thereof) to form a metal oxide precursor solution (suchas an isopropoxide titanium solution). Then, a heating process isperformed to the metal oxide precursor to form a metal oxide (e.g.,titanium oxide) through dehydration and polymerization. In an embodimentwhere water is adopted, for example, the temperature of the heatingprocess ranges from 20° C. to 90° C., and the duration of the heatingprocess ranges from 0.5 hours to 96 hours. However, the invention is notlimited thereto. In some alternative embodiments, the parameter (e.g.,time or temperature) of the heating process is determined based on thetype of the solvent.

In an embodiment, the ligand includes a bidentate ligand or an alkoxideligand. The metal ion is an ion of at least one element selected from agroup consisting of Ba, Co, Cu, Fe, In, Ti, Sn, Sr, V, W, Zn, Mo, Nb, N,Mg, and Al. The bidentate ligand is at least one ligand selected from agroup consisting of acetate, acetylacetonate, carbonate and oxalate. Thealkoxide ligand is at least one ligand selected from a group consistingof methoxide, ethoxide, propoxide, isopropoxide, and butoxide.

The shape of the metal oxide 120 includes, for instance, a granular orfibrous shape. In some embodiments, referring to FIG. 1A, the shape ofthe metal oxide 120 is, for instance, granular. In an embodiment inwhich the metal oxide 120 is granular, the diameter of the metal oxide120 is, for instance, in a range from 1 nanometer to 20 nanometers. Insome embodiments, the ratio of the diameter of the colloidal particleformed by the conductive polymer 110 to the diameter of the metal oxide120 is, for instance, between 5:1 and 500:1. In some other embodiments,the ratio of the diameter of the colloidal particle formed by theconductive polymer 110 to the diameter of the metal oxide 120 is, forinstance, 10:1. In other words, the diameter of the colloidal particleformed by the conductive polymer 110 is greater than the diameter of themetal oxide 120. In some embodiments, the diameter of the colloidalparticle formed by the conductive polymer 110 may be greater than thediameter of the metal oxide 120 by 10 times or more, but the inventionis not limited thereto. In a specific embodiment, the conductive polymer110 is, for instance, PEDOT:PSS, and the diameter of the colloidalparticle formed thereby is, for instance, 33 nanometers, and the metaloxide 120 is, for instance, titanium oxide, tungsten oxide, molybdenumoxide, or vanadium oxide, and the diameter thereof is, for instance,about 3 nanometers. In other words, in the present embodiment, thediameter of the colloidal particle formed by the conductive polymer 110is greater than the diameter of the metal oxide 120 by 10 times or more,but the invention is not limited thereto.

Referring to FIG. 1B, the metal oxide 120 in the composite material 100of the invention is connected to the hydrophilic ends 112 of theconductive polymer 110. In other words, the hydrophilic ends 112 of theconductive polymer 110 may be blocked by the connection to the metaloxide 120. In some embodiments, the metal oxide 120 may block all of thehydrophilic ends 112 of the conductive polymer 110 and expose thehydrophobic ends. In some other embodiments, the metal oxide 120 may beconnected to a portion of the hydrophilic ends 112 of the conductivepolymer 110 and another portion of the hydrophilic ends 112 of theconductive polymer 110 is exposed, but the invention is not limitedthereto. The mole ratio of the conductive polymer 110 to the metal oxide120 may be adjusted based on certain conditions (such as the degree ofconnection of the metal oxide 120 to the hydrophilic ends of theconductive polymer 110). For instance, in some embodiments, the ratio ofthe weight percentages of the conductive polymer 110 to the metal oxide120 is, for instance, between 0.01:1 and 250:1. In a specificembodiment, the conductive polymer 110 is, for instance, PEDOT:PSS, andthe metal oxide 120 is, for instance, vanadium oxide. In the presentembodiment, to connect all of the hydrophilic ends of the conductivepolymer 110 to the metal oxide 120, the ratio of the weight percentagesof the conductive polymer 110 to the metal oxide 120 under suchconditions is, for instance, 0.01:1 to 250:1, but the invention is notlimited thereto.

The metal oxide 120 may be connected to the hydrophilic ends 112 of theconductive polymer 110 in various ways to block the hydrophilic ends 112of the conductive polymer 110. In some exemplary embodiments, the metaloxide 120 is, for instance, connected to the hydrophilic ends 112 of theconductive polymer 110 by a hydrogen bond or a chemical bond (such as acovalent bond). In a specific embodiment, the metal oxide 120 (such as[—V═O] on vanadium oxide) forms a covalent bond (such as [—V—O—SO₂—])with the hydrophilic ends (such as [—SO₃—] on PSS) of the conductivepolymer 110 such that the hydrophilic ends 112 of the conductive polymer110 are blocked to reduce or prevent the reaction with ambient watervapor and oxygen. In other words, the metal oxide 120 of the embodimentis able to prevent the conductive polymer 110 from reacting with ambientwater vapor and oxygen, so as to alleviate deterioration and coatinginconvenience of the conductive polymer 110.

FIG. 2A is a schematic diagram of a composite material shown accordingto some other embodiments of the invention. FIG. 2B is an enlargedschematic diagram of a portion of the composite material shown accordingto FIG. 2A.

Referring to FIG. 2A and FIG. 2B, a composite material 200 includes aconductive polymer 210 and a metal oxide 220, wherein the conductivepolymer 210 has a hydrophilic end 212 and a hydrophobic end 214, and themetal oxide 220 is connected to the hydrophilic end 212 of theconductive polymer 210. The present embodiment is different from theabove embodiments in that the shape of the metal oxide 220 is fibrous.In some embodiments, the ratio of the diameter of the colloidal particleformed by the conductive polymer 210 to the length of the metal oxide220 is, for instance, between 3:1 and 100:1. In some exemplaryembodiments, the length of the metal oxide 220 is, for instance, between5 nanometers and 500 nanometers. In some embodiments, the diameter ofthe colloidal particle formed by the conductive polymer 210 is greaterthan the length of the metal oxide 220. In an exemplary embodiment, thediameter of the colloidal particle formed by the conductive polymer 210may be greater than the length of the metal oxide 220 by 10 times ormore, but the invention is not limited thereto. In a specificembodiment, the conductive polymer 210 is, for instance, PEDOT:PSS, thediameter of the colloidal particle formed thereby is, for instance,about 33 nanometers, the metal oxide 220 is, for instance, titaniumoxide, tungsten oxide, molybdenum oxide, or vanadium oxide, and thelength thereof is, for instance, about 14 nanometers. In other words, inthe present embodiment, the diameter of the colloidal particle formed bythe conductive polymer 210 is, for instance, greater than the length ofthe metal oxide 220 by 2.5 times or more, but the invention is notlimited thereto.

It should be mentioned that, in the composite material according to theembodiments of the invention, the conductive polymers 110 and 210 havethe function of providing the desired conductivity in the overallcomposite materials 100 and 200. For instance, in some embodiments, theconductive polymers 110 and 210 may increase the conductivity of theoverall composite materials 100 and 200. In a specific embodiment, thesheet resistance of the conductive polymers 110 and 210 is, forinstance, between 200Ω/□ and 3000Ω/□, the sheet resistance of the metaloxides 120 and 220 is, for instance, between 200 kΩ/□ and 200 MΩ/□, andthe sheet resistance of the overall composite materials 100 and 200 is,for instance, between 30Ω/□ and 600Ω/□, but the invention is not limitedthereto.

Moreover, in the composite materials 100 and 200 of the invention, theconductive polymers 110 and 210 have the function of maintaining oradjusting the work function in the overall composite materials 100 and200. For instance, in some embodiments, the conductive polymers 110 and210 may maintain the work function of the overall composite materials100 and 200. In some embodiments, the work function of the conductivepolymers 110 and 210 is, for instance, between 4.8 eV and 5.2 eV, thework function of the metal oxides 120 and 220 is, for instance, between5.2 eV and 5.7 eV, and the work function of the overall compositematerials 100 and 200 is, for instance, between the above two workfunctions, such as between 5.0 eV and 5.6 eV, but the invention is notlimited thereto. In other words, the metal oxides 120 and 220 may alsoadjust the work function of the overall composite materials 100 and 200to achieve the desired values.

Formation of the composite materials 100 and 200 includes, for instance,evenly mixing a metal oxide or a precursor thereof and a conductivepolymer in a solvent at the above ratio to produce a conductivepolymer-metal oxide composite material. In some embodiments, the solventincludes a polar solvent, such as water, methanol, ethanol, propanol,isopropanol, butanol, ethylene glycol, diethylene glycol, glycerol,propylene glycol, dipropylene glycol, tripropylene glycol, or acombination thereof. The mixing includes shaking or stirring, and mayfurther include heating or applying ultrasonic waves to facilitatemixing, for example. Specifically, the metal oxide in a solution stateand the conductive polymer in the solution state are evenly mixed. In anembodiment, the mixing may include mixing through oscillation by avortex mixer, mixing through rotation by a rotator mixer, mixing throughrolling by a tube roller mixer, mixing through oscillation by alinear/orbital shaker or a rock shaker, mixing through stirring by a DCstirrer, or mixing through stirring by a magnetic stirrer. In anembodiment, a mixing time is at least one second, and a mixingtemperature ranges from 4° C. to 80° C.

Moreover, in the composite material according to the embodiments of theinvention, since the metal oxide blocks the hydrophilic ends of theconductive polymer, the hydrophilic ends of the conductive polymer donot readily react with ambient water vapor and oxygen, such thatconductive polymer degradation and coating inconvenience are alleviated.Moreover, since the hydrophilic ends of the conductive polymer areblocked, the composite material may overall be hydrophobic in comparisonto the original conductive polymer to increase the adhesion between thecomposite material according to the embodiments of the invention and thehydrophobic material. Moreover, in the composite material according tothe embodiments of the invention, the conductive polymer is located inthe metal oxide. In other words, the metal oxide is dispersed in theconductive polymer such that the metal oxide is not readily aggregated.Therefore, issues caused by the aggregation of the metal oxide can beprevented. Specifically, since the phenomenon of aggregation of themetal oxide is reduced, the film-forming properties of the overallcomposite material can be reinforced, and therefore surface roughnessand surface pinholes, etc., can be reduced so as to prevent powerleakage or corona discharge when an electric field is applied.

Based on the above, the composite material according to the embodimentsof the invention may be adopted in a 3D printing technique of a wetprocess such as ink-jet and aerosol-jet, and may be applied in a plasticsubstrate as a conductive material or a sensing material, the plasticsubstrate may include a polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), polyimide (PI), polyvinyl chloride (PVC),polypropylene (PP), cyclo olefin polymer (COP), or polyethylene (PE).

Moreover, the composite material according to the embodiments of theinvention may also be applied in an organic photoelectric semiconductordevice such as an organic solar cell or an organic light emitting diode.For instance, the composite material according to the embodiments of theinvention may be adopted as an electron or electron hole buffer layer ofa solar cell. Hereinafter, examples in which the composite materialaccording to the embodiments of the invention is applied in a solar cellare described, but the application of the composite material accordingto the embodiments of the invention is not limited thereto.

FIG. 3 is a cross-sectional schematic diagram of an application of acomposite material for a solar cell shown according to some embodimentsof the invention.

Referring to FIG. 3, a solar cell 300 may sequentially include asubstrate 310, a first conductive layer 320, an active layer 330, and asecond conductive layer 340, wherein the first conductive layer 320further includes an electrode layer 322 and a buffer layer 324.Specifically, a first surface 310 a of the substrate 310 is the incidentsurface of a light 302, and the first conductive layer 320 (includingthe electrode layer 322 and the buffer layer 324), the active layer 330,and the second conductive layer 340 are sequentially disposed on asecond surface 310 b of the substrate 310 opposite to the first surface310 a.

In some embodiments, the substrate 310 is, for instance, a transparentsubstrate. The material of the substrate 310 includes, for instance,glass, transparent resin, or other suitable materials. Referring furtherto FIG. 3, the active layer 330 is located on the buffer layer 324. Insome embodiments, the material of the active layer 330 includes, forinstance, poly(3-hexylthiophene) (P3HT) or [6,6]-phenyl-C61-butyric acidmethyl ester (PCBM). The second conductive layer 340 is located on theactive layer 330. In some embodiments, the material of the secondconductive layer 340 includes, for instance, metal. The metal is, forinstance, gold, silver, copper, aluminum, or titanium, but the inventionis not limited thereto.

The first conductive layer 320 is located between the substrate 310 andthe active layer 330. The first conductive layer 320 includes theelectrode layer 322 and the buffer layer 324. In other words, in thepresent embodiment, the electrode layer 322 is located on the secondsurface 310 b of the substrate 310, and the buffer layer 324 is locatedbetween the electrode layer 322 and the active layer 330. The materialof the electrode layer 322 includes, for instance, indium tin oxide(ITO) or indium zinc oxide (IZO), but the invention is not limitedthereto. The material of the buffer layer 324 in the present embodimentmay adopt the composite material 100 or 200 in the above embodiments ofthe invention (refer to FIG. 1A or FIG. 2A). The buffer layer 324 may beformed by spin coating, for example. The application of the compositematerial according to the embodiments of the invention in the bufferlayer 324 of the solar cell 300 can provide good conductivity and thedesired work function, and is suitable for the transfer of electronholes (or electrons). Moreover, since the metal oxide in the compositematerial blocks the hydrophilic ends of the conductive polymer, materialstability can be increased to facilitate coating, and the adhesionbetween the buffer layer 324 and a hydrophobic material can beincreased. Moreover, since the metal oxide in the composite material isdispersed in the conductive polymer, power leakage or corona dischargecaused by the aggregation of metal oxides can be prevented.

The embodiments above apply the composite material according to theembodiments of the invention to the conductive polymer layer of a solarcell. However, the invention is not limited thereto. The compositematerial according to the embodiments of the invention may also beapplied in a sensor.

FIG. 4 is a cross-sectional schematic diagram of an application of acomposite material in a sensor shown according to some embodiments ofthe invention.

Referring to FIG. 4, a sensor 400 of the embodiment includes a substrateSUB, a first electrode 402, a second electrode 404, and a sensingmaterial layer 406. In an embodiment, the substrate SUB may be a siliconsubstrate, a glass substrate, a silicon-on-insulator (SOI) substrate, acircuit substrate, the plastic substrate, or a combination thereof.

As shown in FIG. 4, the first electrode 402 and the second electrode 404are disposed on the substrate SUB. Specifically, the first electrode 402and the second electrode 404 are separated from each other and do notcontact each other. In the embodiment, the first electrode 402 and thesecond electrode 404 may be configured as interdigitated electrodes.However, the invention does not intend to limit the shapes of the firstelectrode 402 and the second electrode 404, as long as a predetermineddistance is provided between the first electrode 402 and the secondelectrode 404, and the first electrode 402 and the second electrode 404are separated without contacting each other. In some other embodiments,the first electrode 402 and the second electrode 404 may also be stackedelectrodes. The three-dimensional configuration of the stackedelectrodes effectively facilitates the density of the sensor and reducethe overall device size. Specifically, the stacked electrode is formedby alternately stacking a plurality of electrode layers and a pluralityof dielectric layers (not shown) vertically on the substrate SUB. Inother words, at least one dielectric layer is interposed between twoadjacent electrode layers to electrically isolate the two adjacentelectrode layers. In an embodiment, the electrode layer includes aconductive material. The conductive material may be a doped or undopedpolysilicon material, a metal material, or a combination thereof. Thematerial of the dielectric layer may be silicon oxide, silicon nitride,or a combination thereof.

In an embodiment, the sensing material layer 406 is located at a gapbetween the first electrode 402 and the second electrode 404 and extendsto cover top surfaces of the first electrode 402 and the secondelectrode 404. While the sensing material layer 406 shown in FIG. 4 doesnot completely cover all the surfaces of the first electrode 402 and thesecond electrode 404, the invention is not limited thereto. In otherembodiments, the sensing material layer 406 may also completely coverall the surfaces of the first electrode 402 and the second electrode404, including the top and side surfaces. It should be noted that, whenan object under test is attached to or contacts a surface of the sensingmaterial layer 406, the object under test may react with the sensingmaterial layer 406. Accordingly, an electrical property, such ascapacitance or resistance, of the sensing material layer 406 between thefirst electrode 402 and the second electrode 404 may be changed. Then,the user may conduct calculation to find out the type of the objectunder test or a parameter variation of the object under test based onthe changed electrical property, such as capacitance or resistance.

In an embodiment, the sensing material layer 406 may be a gas sensinglayer, a light sensing layer, a humidity sensing layer, a temperaturesensing layer, or a combination thereof. In other words, the sensor 400of the embodiment may be configured to sense gas, light, humidity,temperature, or a combination thereof.

In an embodiment, the sensing material layer 406 may be formed bynon-contact printing, for example. In an embodiment, the non-contactprinting includes inkjet printing or aerosol jet printing. Aerosol jetprinting, for example, relies on an aerosol jet deposition head to forman annularly propagating jet formed of an outer sheath flow and an inneraerosol-laden carrier flow. In an annular aerosol jet process, anaerosol stream having the sensing material is concentrated and depositedon the planar or non-planar substrate SUB. Then, through a heating orphotochemical treatment, the sensing material layer 406 is formed. Suchprocess is referred to as a maskless mesoscale material deposition (M3D)process. In other words, the material is deposited without a mask, and amaterial layer after deposition has a line width ranging from 1micrometer to 1000 micrometers.

In an embodiment, the material of the sensing material layer 406 is thecomposite material 100 or 200. Compositions and forming processes of thecomposite materials 100 or 200 are already described in the foregoingand will not be repeated in the following.

In an embodiment, by adopting the composite material 100 or 200 as thesensing material layer 406, the conductive polymer in the compositematerial 100 or 200 can reduce the resistance of the sensing materiallayer 406 and facilitate the sensitivity of the sensor 400. Compared toa known sensor, which adopts a metal oxide as the sensing material layerand is only able to sense at a high temperature (e.g., 200° C. to 400°C.), the sensor 400 of the embodiment is able to sense at roomtemperature (e.g., 0° C. to 50° C.). Therefore, the sensor 400 of theembodiment is applicable in most electronic apparatuses (e.g., cellphones) and does not overheat while significantly reduces the amount ofpower consumption (resulting from the high temperature).

Besides, in an embodiment, the metal oxide in the composite material 100or 200 blocks the hydrophilic ends of the conductive polymer to preventthe conductive polymer from reacting with ambient water vapor andoxygen. Hence, conductive polymer degradation and coating inconvenienceare alleviated. Accordingly, in the embodiment, the lifetime of thesensing material layer having the conductive polymer is lengthened.Besides, the sensing material layer may be coated on the surface of anymaterial (i.e., a hydrophilic or hydrophobic surface) by adjusting thecontent of the metal oxide. Accordingly, the applicability of thesensing material layer is expanded.

In the following, several experimental examples of the invention areprovided in the following to describe the invention in greater detail.Nevertheless, materials and processes described in the experimentalexamples in the following may be suitably modified without departingfrom the spirit of the invention. Hence, the scope of the inventionshall not be limited or interpreted based on the following experimentalexamples.

Experimental Example 1

In Experimental Example 1, PEDOT:PSS (purchased from Heraeus) wereevenly mixed with a metal oxide by a vortex mixer and coated on aninterdigitated electrode. After the mixing, a weight percentage ratiobetween PEDOT:PSS and the metal oxide was 1:1. The metal oxide wasformed by preparing a metal oxide precursor (e.g., molybdenylacetylacetonate) in a concentration ranging from 0.1 wt % to 10 wt % inan alcohol solution (e.g., isopropanol), heating the solution to 40° C.to 80° C., and continuously reacting for 0.05 hours to 96 hours. Then,baking was performed to form a sensing material layer on theinterdigitated electrode. The baking process lasted 10 seconds to 1800seconds, and a baking temperature ranged from 20° C. to 200° C. Then, aresistance value of the sensing material layer of Experimental Example 1was measured, and the result is shown in FIG. 5.

Experimental Examples 2 and 3

In Experimental Examples 2 and 3, the process described in ExperimentalExample 1 is adopted to form sensing material layers on interdigitatedelectrodes. What differs from Experimental Example 1 is that the weightpercentage ratio between PEDOT:PSS and the metal oxide in ExperimentalExample 2 was 2.25:1. The weight percentage ratio between PEDOT:PSS andthe metal oxide in Experimental Example 3 was 6:1. Then, resistancevalues of the sensing material layers of Experimental Examples 2 and 3were measured, and the results are shown in FIG. 5.

Comparative Example 1

In Comparative Example 1, PEDOT:PSS of 1.0 wt % (purchased from Heraeus)was coated on an interdigitated electrode. Then, baking was performed toform a sensing material layer on the interdigitated electrode. Thebaking process lasted 10 seconds to 1800 seconds, and a bakingtemperature ranged from 20° C. to 200° C. Then, a resistance value ofthe sensing material layer of Comparative Example 1 was measured, andthe result is shown in FIG. 5.

Comparative Example 2

In Comparative Example 2, a metal oxide solution of 1.0 wt % (purchasedfrom Sigma-Aldrich) was coated on an interdigitated electrode. Then,baking was performed to form a sensing material layer on theinterdigitated electrode. The baking process lasted 10 seconds to 1800seconds, and a baking temperature ranged from 20° C. to 200° C. Then, aresistance value of the sensing material layer of Comparative Example 2was measured, and the result is shown in FIG. 5.

Comparative Example 3

In Comparative Example 3, a metal oxide solution of 1 wt % was coated onan interdigitated electrode. The metal oxide solution was formed bypreparing a precursor of the metal oxide (e.g., molybdenylacetylacetonate) in a concentration ranging from 0.1 wt % to 10 wt % inan alcohol solution (e.g., isopropanol), heating the solution to 40° C.to 80° C., and continuously reacting for 0.05 hours to 96 hours. Then,baking was performed to form a sensing material layer on theinterdigitated electrode. The baking process lasted 10 seconds to 1800seconds, and a baking temperature ranged from 20° C. to 200° C. Then, aresistance value of the sensing material layer of Comparative Example 3was measured, and the result is shown in FIG. 5.

As shown in FIG. 5, compared with Comparative Examples 2 and 3, thesensing materials layers added with conductive polymer (PEDOT:PSS) inExperimental Examples 1 to 3 have lower resistance values. Besides,compared with the sensing material layer of Comparative Example 1 withonly PEDOT:PSS, the combination of the conductive polymer (PEDOT:PSS)and the metal oxide has an effect of synergism and provides a lowerresistance value. Besides, in Experimental Examples 1 to 3, as thecontent of the conductive polymer (PEDOT:PSS) increases, theconductivity of the sensing material layer decreases, thereby making thesensor more sensitive.

FIGS. 6A to 6D are respectively optical microscopic photos ofComparative Example 1 and Experimental Examples 1 to 3.

As shown in FIG. 6A, in Comparative Example 1 adopting only the metaloxide as the sensing material layer, the sensing material layer ofComparative Example 1 is less formable and prone to generate cracks. Asshown in FIGS. 6B to 6D, as the content of the conductive polymer(PEDOT:PSS) increases, the sensing material layer is more formable andless prone to generate cracks. In other words, adding the conductivepolymer to the sensing material layer not only reduces the resistance ofthe sensing material layer but also prevents the sensing material layerfrom generating cracks.

In view of the foregoing, the composite material according to theembodiments of the invention includes the conductive polymer and themetal oxide, and the metal oxide is connected to the hydrophilic ends ofthe conductive polymer. Hence, in the composite material according tothe embodiments of the invention, in addition to having a desirableconductivity and work function, the hydrophilic ends of the conductivepolymer do not readily react with ambient water vapor and oxygen sincethe metal oxide blocks the hydrophilic ends of the conductive polymer.Therefore, conductive polymer degradation and coating inconvenience arealleviated. Besides, since the hydrophilic ends of the conductivepolymer are blocked, the composite material may overall be hydrophobicin comparison to the original conductive polymer to increase theadhesion between the composite material and the hydrophobic material.Moreover, the combination of the conductive polymer and the metal oxidein the composite material according to the embodiments of the inventionrenders an effect of synergism and may be applicable in the sensingmaterial layer of a sensor to effectively reduce the resistance of thesensor while facilitate the sensitivity of the sensor. Furthermore,adding the conductive polymer to the sensing material layer not onlyreduces the resistance of the sensing material layer but also preventsthe sensing material layer from generating cracks. Therefore, thereliability of the sensor is enhanced.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

What is claimed is:
 1. A method of manufacturing a composite material,comprising: providing a conductive polymer having a hydrophilic end; andadding a metal oxide, such that the metal oxide is connected to thehydrophilic end of the conductive polymer, wherein the metal oxide isobtained by subjecting a metal oxide precursor to a dehydrationreaction, a polymerization reaction, a condensation reaction, or acombination thereof.
 2. The method of manufacturing the compositematerial as claimed in claim 1, wherein the conductive polymer isdispersed in a solvent to form a colloidal particle, and a diameter ofthe colloidal particle is between 10 nanometers and 500 nanometers. 3.The method of manufacturing the composite material as claimed in claim2, wherein a shape of the metal oxide is a granular shape.
 4. The methodof manufacturing the composite material as claimed in claim 3, wherein adiameter of the metal oxide is between 1 nanometer and 20 nanometers. 5.The method of manufacturing the composite material as claimed in claim4, wherein a ratio of the diameter of the colloidal particle formed bythe conductive polymer to the diameter of the metal oxide is between 5:1and 500:1.
 6. The method of manufacturing the composite material asclaimed in claim 2, wherein a shape of the metal oxide is a fibrousshape.
 7. The method of manufacturing the composite material as claimedin claim 6, wherein a length of the metal oxide is between 5 nanometersand 500 nanometers.
 8. The method of manufacturing the compositematerial as claimed in claim 7, wherein a ratio of the diameter of thecolloidal particle formed by the conductive polymer to the length of themetal oxide is between 3:1 and 100:1.
 9. The method of manufacturing thecomposite material as claimed in claim 1, wherein the metal oxideprecursor is in the form of solution, and the metal oxide precursorcomprises at least one metal ion and a ligand.
 10. The method ofmanufacturing the composite material as claimed in claim 9, wherein theligand comprises a bidentate ligand or an alkoxide ligand.
 11. Themethod of manufacturing the composite material as claimed in claim 10,wherein the bidentate ligand is at least one ligand selected from agroup consisting of acetate, acetylacetonate, carbonate and oxalate, andthe alkoxide ligand is at least one ligand selected from a groupconsisting of methoxide, ethoxide, propoxide, isopropoxide, andbutoxide.
 12. The method of manufacturing the composite material asclaimed in claim 9, wherein the metal oxide precursor comprising themetal ion and the ligand be dissolved in a solvent containing anauxiliary agent to form a metal oxide precursor solution, and theauxiliary agent is an acid, an alkali, an oxidizer, or a combinationthereof, the solvent is water.
 13. The method of manufacturing thecomposite material as claimed in claim 1, wherein the conductive polymercomprises a conjugated polymer and an acidic solubilizer.
 14. The methodof manufacturing the composite material as claimed in claim 13, whereinthe conjugated polymer is a main conductive structure, and theconjugated polymer comprises poly(3,4-ethylenedioxythiophene) (PEDOT),polyphenylene sulfide (PPS), polypyrrole (PPy), polythiophene (PT),polyaniline (PANI), or a combination thereof.
 15. The method ofmanufacturing the composite material as claimed in claim 13, wherein theacidic solubilizer comprises poly(styrensulfonate) (PSS), acetic acid,propionic acid, butyric acid, benzoic acid, or a combination thereof.16. The method of manufacturing the composite material as claimed inclaim 1, wherein the metal oxide is connected to the hydrophilic end ofthe conductive polymer by a hydrogen bond or a covalent bond.
 17. Themethod of manufacturing the composite material as claimed in claim 1,wherein evenly mixing the metal oxide obtained from the metal oxideprecursor or the precursor thereof and the conductive polymer in asolvent to produce a conductive polymer-metal oxide composite material,and the solvent comprises a polar solvent.
 18. The method ofmanufacturing the composite material as claimed in claim 17, wherein thepolar solvent comprises methanol, ethanol, propanol, isopropanol,butanol, ethylene glycol, diethylene glycol, glycerol, propylene glycol,dipropylene glycol, tripropylene glycol, or a combination thereof.